Specification matching is a way to compare two software components based on descriptions of the components' behaviors. In the context of software reuse and library retrieval, it can help determine whether one component can be substituted for another or how one can be modified to fit the requirements of the other. In the context of object-oriented programming, it can help determine when one type is a behavioral subtype of another. We use formal specifications to describe the behavior of software components, and hence, to determine whether two components match. We give precise definitions of not just exact match, but more relevantly, various flavors of relaxed match. These definitions capture the notions of generalization, specialization, and substitutability of software components. Since our formal specifications are pre- and post-conditions written as predicates in firstorder logic, we rely on theorem proving to determine match and mismatch. We give examples from our impleme...

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Given a software library whose components are represented by formal specifications, we distinguish between two types of retrieval procedures: exact retrieval, whereby, given a query K, we identify all (and only) the library components that are correct with respect to K; approximate retrieval, which is invoked in case exact retrieval fails, and which (ideally) identifies the library components that minimize the required adaptation effort (once such a component is retrieved, the effort of adapting it to satisfy query K is minimal over the set of all the components of the library). To this effect, we define four measures of functional distance between specifications, and devising algorithms that minimize these measures over a structured set of components; then we discuss to what extent these measures can be used as predictors of adaptation effort. Correspondence author. 1 Exact Retrieval and Approximate Retrieval Software libraries are repositories where software components can be ...